On the previous version I could swipe left or right to start with my camera, or just unlock the phone. I just got the Ice Cream Sandwich update and now I can swipe up or down to access the dialer or my text messages. Can I customize this at all? I'd love to have more apps accessible from the lock screen, and I'd also like to change from the default text message program.

Depends entirely on what ROM your are running, it's not a feature that's usually available in stock ROMs as far as I know. If the feature is not there under settings, you just need to find a ROM for your phone that has that feature.
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pzkpfwJul 3 '12 at 18:14

For the One Plus One Phone running Android Version 4.4.4 with CyanogenMod version 11.0-XNPH44S, go to Settings -> Lock Screen -> Slider Shortcuts.

You will just see the icon of the lock and after you touch it, you will see your current options. To change or remove one of these, move the lock to the target icon and you will then see options to modify it.